Natural buoyancy, four strong pistons & a snorkel! 
Few weeks back I was on boat safari, at backwaters of Kabini. As we had good rains that lasted long this year, the lake was full and not many animals were coming to the water.
By evening we had seen couple of crocs basking in the evening sun soaking up energy as much as they can, a few herds of chital, a pair of Malabar Pied Hornbills and lots of Barn Swallows roosting on the dead tree stumps in the river. As we started heading back, Byra, our boatman, spotted a herd of eight Elephants on Bandipur side. We went closer, switched off the engine, and started drifting towards the land, but little away from the herd. The Elephants were not much aware of us initially as the wind was blowing towards our direction. But as we were about 20mts from them they went behind the bamboos. After just a minute or so, as we dint start they came back to the river, started drinking and spraying. There were two calves playing in the water too.
As we were watching, one of them slide and dived into the river, Byra said they might cross the river! 'I doubt it' I said as there is water everywhere, backwater is full and the other side forest is over half a mile! Before I finished thinking, one after another, they all dived and started swimming! Wow! I have seen them swimming in small water holes, and had heard about this river crossing here and of course the swimming at sea between Islands at Andaman & Nicobar. But now its right in front of me! Sometimes its hard to believe but natural buoyancy , four strong pistons & of course a snorkel ! What else does a 3-ton animal need to swim easily? I could see them wobbling, whole body being submerged sometime only head and trunk visible, spraying water and making loud noise. Its something like watching whales!
One of the calf which was just a year old was so much at ease! The herd took around 20mins to swim across over half a mile and safely reach Nagarhole. As we followed, they all ran into the forest, except for one who waited for the last one to reach the shore.. as with the last one there was a calf!
It was one of the best Elephant sightings I have had and as summer comes, I would witness more of this.